Fluid dispensing systems are generally used to mix two components to form a desired mixture. In many applications, it is necessary to precisely control the amount of each component that is added to form the mixture. Such fluid dispensing systems are often used to form an epoxy, acrylate, polyurethane or silicone that can be used as an adhesive. The process of polymerization is called “curing” and can be controlled through temperature, choice of resin and hardener compounds, and the ratio of these compounds. The choice of temperature, resin and hardener can result in the curing process taking minutes to hours. Some formulations benefit from heating during the cure period, whereas others simply require time and ambient temperatures.
These adhesives typically require a precise mix of the two components that are mixed together to form the desired third chemical. Depending on the properties required, the ratio may vary from 1:1 or over 10:1. However, in order for the final product to be a precise formulation, the resin and hardener must be mixed at an exact ratio. Until they are mixed the two components are relatively inert, although the “hardeners” tend to be more chemically active and require more protection from the atmosphere and moisture. The rate of the reaction can be changed by using different hardeners, which may change the nature of the final product, or by controlling the temperature.
Prior art volumetric systems for mixing two fluids (e.g., a resin and a hardener) at an exactly prescribed ratio suffer from the problem that the metering of the material is located at significant distances (1-2 meters or more of tubing) from the application dispense point. This causes fluctuations in ratio control resulting in inexact mixing of the two components and, consequently, unacceptable variances in the bonding strength of the adhesive. The prior art systems perform the mixing more like a pressure-time dispense system than a true volumetric mixing system, which is critical for accurate ratio control. Accordingly, there is a need for a dispense system that accurately mixes the two components at a precise ratio in order to provide a mixture with the desired chemical composition.